不同抽气速率下真空超声波对生菜内部大肠杆菌的去除效果及其品质变化

Effects of Vacuum Ultrasonic Cleaning with Different Evacuation Rates on the Removal of Escherichia coli inside Lettuce and its Quality Changes

摘要:

真空预冷过程会导致致病菌渗透至蔬菜气孔内部,且无法通过常规清洗方式去除。为了去除已渗透至生菜气孔内部的大肠杆菌(E.coli),选用三种抽气速率α1 (0.4673/min)、α2 (0.3235/min)和α3 (0.1617/min)下的真空超声波(VC-US)复合清洗剂来进行清洗,通过测定清洗前后的菌落数量及相关理化指标在贮藏过程中的变化,评价其对生菜内部E. coli 的清洗效果和对品质的影响。结果表明:α3组处理后,生菜内部的E. coli数量从原始的4.33下降至1.47 log10 CFU/cm2,优于α1和α2组(分别下降至2.03和1.92 log10 CFU/cm2) (P<0.05)。贮藏2 d后,α3组的L*值和b*值显著低于α1组(P<0.05),a*值则略高于α1组,但均与α2组无显著性差异(P>0.05)；三种不同处理方式后的叶绿素和维生素C的含量均无显著性差异(P>0.05)；此外, α3组的失重率(-19.89%)显著低于α1组(-0.18%)和α2组(-19.03%) (P<0.05)。综上所述,较低抽气速率下的VC-US清洗方式能更有效地去除生菜内部的E.coli,且对品质无显著影响,旨在为VC-US技术在蔬菜内部致病菌的去除提供理论依据和应用价值。

Abstract:

Vacuum cooling often results in the penetration of pathogenic bacteria into the internal stomata of vegetables, making conventional washing methods ineffective. To remove E. coli that penetrates the stomata of lettuce, a vacuum-ultrasonic (VC-US) composite cleaning method was applied at three evacuation rates: α1 (0.4673/min), α2 (0.3235/min), and α3 (0.1617/min). Effectiveness and impact on lettuce quality of VC-US were evaluated by measuring the colony counts and related physicochemical indicators before and after cleaning, as well as their changes during storage. Results showed that the α3 group reduced E. coli counts inside lettuce from 4.33 to 1.47 log10 CFU/cm2, which was significantly better than that of α1 (to 2.03 log10 CFU/cm2) and α2 groups (to 1.92 log10 CFU/cm2), respectively (P<0.05). After 2 d of storage, the L* and b* values of the α3 group were significantly lower than those of the α1 group (P<0.05), while the a* value was slightly higher, but there was no significant difference compared to the α2 group (P>0.05). Chlorophyll and vitamin C contents showed no significant differences among the three treatment groups (P>0.05). Additionally, the weight loss rate in the α3 group (-19.89%) was significantly lower than in the α1 (-0.18%) and α2 groups (-19.03%) (P<0.05). Collectively, our study indicated that VC-US cleaning with a lower evacuation rate is more effective in removing E. coli inside lettuce without significantly affecting its quality. Thus, providing theoretical support and practical value for the application of VC-US technology in removing internal pathogens from vegetables.